Hull flex...good, bad, indifferent?

was refering to folding kayaks
most of which are beamy and handle rough water well.

Sorry, I should have made that more clear.

No one is trying…

– Last Updated: Feb-24-06 9:00 AM EST – make Celia feel she has to defend her choice of boat(s). All we're pointing out is that the assertions made about heavy layups by some British companies are untrue. Whether it's due to ignorance or deception is debatable, but facts are facts. Lighter, more resilient boats can be as strong or stronger and more durable than the back-breakingly-heavy "traditional" British boats. No one here has criticized the performance of these boats and like you, some of us own them specifically because they DO perform well. That doesn't mean that they can be made better.

What difference does it make? For paddling under easy to moderate conditions, it probably doesn't matter. However, construction affects durability, which affects safety when you're playing in the rough stuff. You've pushed the envelope and done enough damage to boats over the years to know this from firsthand experiece. You've seen other paddler's boats nearly broken in half. Would you not rather be paddling a boat that would survive severe use better?

On an even more practical level, lighter boats are easier to carry and transport. Would you not prefer to hoist a 45 pound boat onto your car than a 60 pound boat?

You've special ordered boats with "elite" layups in order to reduce weight and get away from chopped-strand mat construction (that's what you told me), so these things evidently do matter to you.

Why discuss this? WE are the ones paying for these products and we have the right to demand high-quality, durable boats of reasonable weight. Consumer demand has obviously been a driving factor in P&H and VSK upgrading their layups with superior materials and construction techniques, creating stronger, lighter, higher-quality boats. That certainly seems like a good thing, doesn't it? If we had not complained about material, construction and quality issues, they'd probably still be producing the same boats that they did 10 years ago. When one manufacturer upgrades their products, it forces their competition to do the same and ALL consumers benefit.

A modest question
As long as this is a food fight, might as well roll a grenade in the room. Is there a downside to overly thick gelcoat? My understanding is gelcoat is quite hard and brittle. While this makes it resistant to scratches, does it also make it more likely to be damaged by having chunks chip off due to an impact if it is too thick?

Wow, unusual Jed post…Bnystrom yep
I paddle and have paddled Brit boats and like em. As Peter from Valley has stated in past posts, the old build technology is adequate for the use requirements, so no one should feel bad about buying such a boat.

But, the facts are, there are superior construction techniques and materials available, and we’ll see those applied to our industry. Already are seeing this… Sorry if we touched a nerve Jed.

Educational thread
For the past few years I’ve had the honor of working with aerospace and maritime composite engineers. I’ve been tasked with destructive on the water testing of boats from several manufacturers. The results have been eye opening to me and I’ve learned a lot. I’ve also has to let go of inaccurate dogma I once held. My modern infused, cored, carbon glass boat that’s 45 lbs. has held up to incredible abuse and fared better than any boat I’ve owned. The future will bring us lighter, stronger boats. Wife paddles a 15 ft. prototype that weighs 30 lbs. and is crazy strong!


– Last Updated: Feb-24-06 5:35 PM EST –

Salty, with regard to "striking a nerve": If I came on a bit strong it's because the ultimate question is about more than what's the best material or the best construction technique. It also needs to consider the preferred mode of failure, durability relative to hard use as well as all the other issues that are affected by the choices of material and construction technique.

You certainly understand the complexities involved and yet you let slip a slight about the Brits convincing their fans that heavy and strong are the same thing. I saw this comment as a cheap shot to those that own Brits boats. While I seem to remember that you paddle a Brit boat often, the posts here are read by people that don't know you or me or what our equipment choices and preferences might be.

To the original poster:

Stiff hull construction allows the use of rigid bulkheads that often remain dry after years of abuse and heavy thick gel-coat layers that provide for significant and long-term abrasion protection. Stiff hull construction does not require the latest and greatest in materials and in fact benefits little from the use of such materials since the most common way to stiffen composite material is by making it thick in cross section. Note the thickness of the gel-coat is not just for abrasion resistance but also to protect the glass mat from the intrusion of moisture. Stiff hull construction creates a heavy boat that will endure significant abuse, last a long time and when damaged is easily repaired.

Flexible hull construction requires flexible bulkheads (that are prone to leakage), requires a thin gel-coat layer to avoid (but not eliminate) flaking of the gel-coat. Flexible hull construction allows the use of much lighter materials and offers significant weight savings. Flexible hull construction creates a light and strong boat that if handled gently will last a very long time but when damaged will require a more extensive repair. Either hull design will last for more years than the paddler's interest will as long as the boat receives moderate care and protection from sun.

Flexible hulls handle impact by absorbing the forces across a large and flexible area. Flexible hulls can take a significant amount of abuse before failure but when they fail they do so catastrophically. Refer to Pat's hammer-on-the-hull video to see the kind of abuse a (bare) flexible hull can withstand. But note that it is a bare hull in the video and not a complete boat. I'll be happy to reveal the showmanship aspect in Pat's video when he lets me swing the hammer on a completed boat. Flexible hulls are hard to hole but if the hit is hard enough the whole hull / section is affected requiring a larger, more extensive and more difficult repair. A repair of a flexible hull will result in reduced flexibility at the repair site leading to stress risers and a repair that is less strong than the original hull.

Stiff hulls protect against impact by attempting to be monolithic. The idea is to bounce off most impacts. Moderate impacts might scratch the gel-coat but rarely do structural damage. The force from a significant impact will be concentrated at the point of impact and will likely result in a hole but the damage is localized and is easily repaired with simple tools and materials. Once repaired the hull is a strong as before the damage (albeit somewhat heavier).

Yes, I've seen (and been the implement of) more than my share of damage to boats with both stiff and flexible hulls. In a perfect world, I'd choose a flexible hull ( to limit holing & save weight) with rigid sections (to limit the possibility of catastrophic failure), waterproof bulkheads, a rigid bulkhead for a foot rest, significant abrasion resistance and that weights-in about 40#. But such a beast does not exist and current technology doesn't let anyone create such a combination of mutually-exclusive properties in one boat.

Bottom line is that if I know I'm going to be banging up against rocks all day I'll take the plastic hull. If I know I'm going to put the boat into harm's way in significant conditions then I want the stiff hull. If I think I can avoid any real impact and will be able to "baby" the boat then I'll take the flexible hull.



gel coat sucks. Get a boat with S-glass
for the outer two layers, and forget about the gel coat.

Stand by what I said
Brit boats! I’m an advocat of them…always support them as great designs. But the fact is they are, for the most part very crudely made boats. I’ve accepted that as a minor set back to an overall great product. No boat is perfect. I’ve paddled superior lay-ups in designs that don’t do it for me.

So, like any good dealer or sales person, you focus on the positives. The boats are tough overall, and do their job well, easy to fix etc.

Most Brit boat enthusiasts will explain that weight as a strength thing, which I think illustrates my point about effective marketing.

BUT, to infer that more modern, lighter lay-ups are not as tough is blatantly false. I agree with G2d about Gel-coat. No structural value, heavy. I would not have it on a custom boat for me. Of the Brit boats P&H was ahead in construction, and we’ll see Peter and his partner bring Valley construction up a lot with better boats in the future.

I would never not recommend an older Brit boat! I just wouldn’t BS someone about how they are made. Happy paddling.

I would venture heavy ‘brit’ layups

– Last Updated: Feb-26-06 4:15 AM EST –

NOT a means to an end ....... figure yes they always built them like this because the expedition guys used them hard, so why change since folks back then were not so concerned ( possibly) w/ weight like today. Was not there so only speculating ..... no excuse for overly isotropic, resin rich stuff coming out recently though. Want to build the cheapest glass boat possible? One that unskilled labor can do without thinking ? Use Mat. Anyone can bucket and brush .... hard to miss the mold + the mat just keeps on soaking up all you can throw at it .... whoo hoo even 'stronger' now.

Response # 1 to Celia's initial post ..... dang it. Why do these things sometimes get posted out of order ?

Dang Jed, do you really believe there

– Last Updated: Feb-26-06 4:32 AM EST –

there would not be a positive difference in performance between a 60 pound Explorer and a 40 pound one ??? FYI Your use of the them " resin injection" is incorrect.

I to believe folks first look to the design then construction ( if at all) comes next . Still having trouble figuring out the "Elite" layup ( talk about making people feel bad about their 'commoner' standard glass lay up ) for an extra what is it ?? 800 or something now ?
THATS marketing B.S.

Response to "Engineer" post.

Nice one eel … The thicker the
gelcoat, the bigger the chip thats gonna fly off it upon impact. Flaking is another thing altogether. There are much better quality gelcoats around that have better characteristics and can endure a little more bending even though they are basically not meant to flex too much. Proper bonding to glass has ALOT to do with how well the gelcoat stays put too. Let it cure too much, moisture in air or spray equipment are some of the problems that could go undetected / unanswered resulting in less than optimum bonding ( to glass) as the boat gets layup up.

Right on G2d with the S-glass first
two plys.

Thicker gelcoat might take a little
deeper scratching but still nothing to really worry about. Especially with a mat built hull.

The one thing about mat is it is resin rich and unless the mat is blasted from something, you really do not even have to think about it. Even then unless you were keeping it in the water non-stop in a slip or like… whatever moisture gets into laminate is gonna dry out once the boat is out of the water… these ( kayak / canoe) hulls are just not that thick for this kind of worry. Still would like to see what happens when water FREEZES in laminate though… couldn’t be good.

It is routine practice for huge chemical tanks to first be layed up with two or more plys of resin rich mat as a moisture barrier… this is on the chemical contact side.

More about mat getting dameged somewhere else in this thread.

Hey Salty, we have some fully rigged
25 pound boats that you can stand on.

Totally agree with Nick S. …
I would venture the gelcoat is thick not because of their intentions of extra durability.

Rather a byproduct of brushing it in… when brushing gelcoat, there is no way to do it thiner than spraying and have it come out proper… Pour it in and smear around … since it has a tiny bit of ‘flow’ this is why the keel ends are sooo thick.

Throwing arms up in the air…

– Last Updated: Feb-26-06 5:46 AM EST –

Never intended to put on a 'show' ...... sheesh .... WHAT ELSE CAN I DO ? I am HAMMERING that hull as hard as I can ..... when nothing happens, I flip the hammer around and hit it with the claw. That is years 'training' building my own stuff and frustration nukeing out @ the thought of boats still being built of mat.

All kidding aside ...... No mat hull is going to endure something like that. To be honest, I did not have a whole boat sitting around waiting to be hammerd so I had to make do. The argument about the hull flexing just does not fly with me as the force is coming on so rapidly and with concentrated psi all focused like a gunshot..... still no damage. Wanna flip a mat boat over and try it ? This is what would happen. The gelcoat would fly off and the damage ( from first impact) might not show too much .... certainly it would on the inside of the hull as a large whitish spot as the not very strong mat as had the resin disloged from its matrix of unoriented strands. Damage radiates outward in all directions .... all hits after would continue to further damage layup to where a single spot has grown huge and eventually turns to dust ( fiberglass) literally.
Anyone who has ever owned or repaired an older fiberglass boat can attest to a simple " oops, came in too hot and hit the dock doesn't look so bad" spot on a weekend will grow to over 12 times it actual size as the prep for repair begins.

For what its worth, we have been building sub 40 pound fully hatched, bulkheaded, adjustable seat boats for quite some time now.
To answer the original poster, we strive to build the stiffest boats possible as we believe this is the best for performance. Our boats are strong, stiff and will yield rather than breaking down upon both minor AND major impacts. Using epoxy has alot to do with this as well.

In the field stupid boat tests ..... boat came out unscathed.

Walking straight into a telephone pole while shouldering boat.
Attempting to drive slow with boat on roof with no straps .... boat walks off, takes out mirror before hitting pavement.
And the best all time (IMO) brutal tests of one of my boats was losing control of a brand new one while lowering it off a 12' rooftop and having it's belly slam r i g h t ONTO the corner of a boat trailer.... gouge but zero structural damage. This was a whole boat Jed.

Necky AC Layup
Great thread. Lots of good comments and interesting perspectives.

What has been the feedback on the Necky AC construction so far? Seems like a ton of money for a few pounds but other than that, what do you see and hear?

Crazy strong!
Initial problems with gel-coat being too brittle and not adhering well, resulting in cracks and some peeling. That issue has been fixed. Those boats are infused with soric coring and are overbuilt. Try standing on the deck of your NDK! Not that you would, thus the overbuilt comment. I believe the infused Necky’s built now are some of the strongest kayaks built. I’ve seen some Nimbus boats and Seaward boats recently that looked very well made as well. I have a proto Chatham that has gel coat cracks all over and has been absolutely abused. Still structurally sound.

BTW, average weight of gel-coat on a kayak is upwards of 6 lbs.

Very cool
What core are you using? Soric, Divinycell? Recently did some detructive tests on some infused lay-ups which were Carbon/Polyester co-weave, glass, Kevlar, and gosh was that co-weave tough!!! It resisted tearing far more than the inner Kevlar layer. I was amazed. So many cool materials and options out there!

6 pounds!!??
Whoa! And that’s average? Wow. I didn’t know that. I shouldn’t be surprised as I learned how ounces turn to pounds while building my Pygmys. But 6 pounds…

What about abrasion resistance on the Neckys?